簡單的結構體排序，程式碼如下

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <map>
#include <cmath>
#include <queue>
#include <cmath>
#include <ctype.h>
#define ll long long

using namespace std ;

typedef struct{
    int id ;
    int grade ;
}meassage ;

bool cmp( meassage a , meassage b ){
    if ( a.grade == b.grade ){
        return a.id < b.id ;
    }
    return a.grade > b.grade ;
}

int main(){
    meassage mea[5005] ;
    int n , m ;
    cin >> n >> m ;
    for ( int i = 0 ; i < n ; i ++ ){
        cin >> mea[i].id >> mea[i].grade ;
    }
    sort(mea , mea + n , cmp) ;
    int grade_line = mea[int(floor(m * 1.5) - 1)].grade ;
    int tot = 0 ;
    for ( int i = 0 ; i < n ; i ++ ){
        if ( mea[i].grade >= grade_line ){
            tot ++ ;
        }
    }
    cout << grade_line << " " << tot << endl ;
    for ( int i = 0 ; i < n ; i ++ ){
        if ( mea[i].grade >= grade_line ){
            cout << mea[i].id << " " << mea[i].grade << endl ;
        }
    }
    return 0 ;
}